For an optical encoder to work optimally, the distance between the system's codewheel, emitter, and detector must be controlled. Current encoder packages that are intended for quick assembly use a variety of methods for setting the gap between the emitter/detector and codewheel.
One prior art method uses a shim of controlled thickness that the codewheel is pushed against during assembly. After the distance is set, the shim is removed. The assembly time required is relatively long and it is necessary to provide the user with a gapping shim that is disposed of after assembly.
A second prior art method, shown in FIGS. 1 and 2, uses a mechanical mounting feature connected to cams. During assembly, the codewheel is pushed against the mechanical feature, after which the feature is moved away from the codewheel by twisting the cam. During operation, the codewheel must be able to rotate freely so any mechanical feature used to control the gap must be removed after installation. This manufacturing method is faster than the shim method but it too can require extra cam parts that are not used during operation. The system shown in FIG. 2 can result in poor contact between the housing and a cam on the base of the encoder that will impact performance of the encoder because of emitter/detector misalignment.